Figure 15-10 Memorabilia in Space (a) Humans have beamed radio signals into space, hoping that the message will someday be intercepted by an alien civilization. This is a visual version of the signal sent in 1974 from the Arecibo radio telescope toward the globular cluster M13. The Pioneer and Voyager spacecraft, now in interstellar space, also carry messages from Earth. (b) The plaques on Pioneer 10 and Pioneer 11 provide information about where humans are, what we look like, and some of the science we know. (c) Images and sounds sent on Voyager 1 and Voyager 2 were stored on phonograph records, long before DVDs were even a twinkle in an engineer’s eye. There are also instructions for playing the record, which contains information about our biology, our technology, and our knowledge base. Each record also contains the sounds of children’s voices. It is remotely possible that another race might someday discover the spacecraft.